Gunmen opened fire on a gathering of Afghan Muslim clerics in the southern province of Helmand, killing seven people, police said on Wednesday.

The Ulemma Council, the highest religious authority in a deeply conservative country, came under attack after it had repeatedly announced its support for security forces fighting the hard-line Islamist Taliban insurgents.

"The meeting was ongoing when two Taliban gunmen attacked the gathering," police official Jan Aqa said.

Four civilians and three police were killed and seven people wounded in the attack in Lashkar Gah, the provincial capital.

One gunman was killed and another was still fighting with security forces, Aqa added.

The Afghan Taliban, ousted from power in 2001 by US-led forces, have been fighting to bring down the US-backed government in Kabul, and stepped up attacks after most foreign forces pulled out at the end of last year.

Qari Yousuf Ahmadi, a Taliban spokesman, claimed responsibility for the attack and said 15 officials were killed. The insurgents often exaggerate number of casualties they inflict.

Helmand province has been the scene of number of deadly attacks by the Taliban.

Numbering some 3,000 clerics and scholars and headed by a 150-strong National Council, the powerful Ulemma can sway public opinion significantly through mosques across the country that are still main source of Afghan social cohesion.

Taliban insurgents have stepped up their attacks against Afghan forces since they announced their "spring offensive" last month.